1. Field of the Invention
The present invention relates to an apparatus and a method for image forming, and in particular, it relates to an apparatus and a method for image forming that store and print or display input documents or images.
2. Description of the Related Art
It has become common practice for companies to make documents printed on paper or the like into electronic form to challenge the information sharing and to solve the problem of storage space.
Digitalizing an enormous volume of print documents and storage them in specific in-company servers etc. allow information sharing and easy accesses to the electronic information as needs arise. Also, digitalizes documents can be freely output in the form of hard copy, so that there is no need to store original print documents, contributing to the reduction of storage space.
However, all documents are not always digitalizes in practice. For example, it is still general to store what-is-called original copies of tax documents, financial statements, etc. (hereinafter, referred to as tax/finance-related documents) in the form of paper without being digitalizes in companies or the like.
This is because there is a legal limitation, and, from a technical point of view, there is no sufficient technique to read the only one original copy with higher reproducibility than for general documents, and print the read electronic information with high reproducibility.
A more important point is that, for image forming apparatus including scanners, a technique of data security, such as confidentiality and prevention of tampering, has not yet been developed and applied sufficiently.
However, in recent years, the technique of high-resolution and high-color-reproducibility of image forming apparatus such as scanners has made remarkable progress, and a security technique for improving confidentiality and preventing tampering has also made great advance. From a technical viewpoint, this has decreased the necessity of storing original paper copies by digitalizing the originals of tax/finance-related documents and storing and managing them as electronic originals.
In response to the progress of the techniques, there is a legal tendency to approve electronic documents of part of tax/finance-related documents as electronic originals.
To digitalize paper originals to generate electronic originals, it is important to develop not only a technique of preventing tampering of electronic originals but also a technique of preventing tampering of paper originals in advance.
One of the techniques of preventing the tampering of paper documents is a technique of applying a special pattern on the base of the original to distinguish the original from copies. The effect of the pattern is increasing the visibility of specific concealed characters in the copies, which are inconspicuous in the original with naked eyes. The techniques distinguish the original from copies using this effect.
There is also an application of this concept; a technique of printing a pattern with a printer. For example, JP-A 2004-280603 discloses a technique of printing a pattern so as to cover addresses, names, etc. when printing public documents such as a resident's card, whereby, when they are copied, making specific characters come to the front.
The digitalization of documents such as tax/finance-related documents requires a technique with higher data security and higher reproducibility than for general documents.
Specifically speaking, the digitalization of tax/finance-related documents requires the function of reading paper originals before digitalizing so as to check for tampering with white-out, and displaying the corrected marks on a display or printing it with a printer so that it can easily be identified.
When corrected marks can be viewed in the image forming apparatus, tampering to the original can be prevented and generation of an electronic original based on the tampered document can be prevented.
The white of white-out is generally whiter (lighter) than that of the base of documents (the color of paper). This requires the function of reading also the white of high-lightness of white-out etc.
On the other hand, the technique of reading and digitalizing general documents has the function of reading the documents such that the white of the base of the documents (the color of the documents) become inconspicuous to prevent the white of the base from looking like a stain.
Specifically speaking, a saturation characteristic is provided by setting the gradation characteristic of scanners appropriately, the saturation characteristic preventing the white lighter than the base of a document from becoming lighter than the base of the document. Thus, the white of the base of the document can be as light as that of the print paper. This process (hereinafter, referred to as “general base processing”) prevents the white of the base of the document from coming to the front of the print document, providing a clear print document.
The “general base processing” adopts the process of saturating lightness higher than that of the white of the base of documents. Accordingly, information on high-lightness white such as white-out is lost during reading, and so cannot be read.
Thus “special base processing” is required which does not saturate even lightness higher than that of the white of the base.
Furthermore, even after reading a document without saturating high-lightness white of white-out etc., the corrected marks with the white-out sometimes disappear depending on subsequent image processing, particularly, density conversion processing. For example, when the density (lightness) of the corrected marks is set higher than the white of print paper, the white is saturated by the white of the print paper, so that the corrected marks disappear. The white of corrected marks can be made conspicuous by decreasing (darkening) the entire density. In this case, however, the part other than the corrected marks also becomes dark throughout, resulting in illegible print output.
Accordingly, image processing that increases the contrast of corrected marks locally is required.
Even if image data that is read without saturation of corrected marks can be generated, the corrected marks can be removed in principle through intended tampering on the image data, for example, intended alteration of gradation processing during the generation. Thus a system of preventing intended correction or removal of the read corrected marks is also required.